Download Nervous and Endocrine System

Intro
• Two systems coordinate communication throughout the body: the
endocrine system and the nervous system
• The endocrine system secretes hormones that coordinate slower but
longer-acting responses including reproduction, development, energy
metabolism, growth, and behavior
• The nervous system conveys high-speed electrical signals along
specialized cells called neurons; these signals regulate other cells
© 2011 Pearson Education, Inc.
The nervous system
Chapter 48 and49
#1: The Nervous System Function
Figure 49.4
Central nervous
system (CNS)
Brain
Peripheral nervous
system (PNS)
Cranial nerves
Spinal cord
Ganglia outside
CNS
#2
Spinal nerves
# 3 – The structure of a neuron
# 4. Types of Neurons
• The nervous system is made up of cells called
neurons.
• Sensory neurons: transmit nerve impulses from receptors
to the central nervous system.
• Motor neurons: transmit nerve impulses from the CNS to
effectors
• Interneurons: transmit
nerve impulses between
sensory neurons and
motor neurons.
Figure 49.3
Quadriceps
muscle
Cell body of
sensory neuron in
dorsal root
ganglion
Gray
matter
White
matter
Hamstring
muscle
Spinal cord
(cross section)
Sensory neuron
Motor neuron
#5 Reflex arc
Interneuron
#5 Reflex arc
#6 – How a nerve impulse travels through the
neuron.
• When a nervous system receptor is in its resting potential, there is a
difference in voltage (charge) between the inside and outside of the
cell – this is generated by ion pumps and ion channels. The difference
in voltage across the membrane is called the potential difference.
• The potential difference when a cell is at rest is called its resting
potential. When a stimulus is detected, the cell membrane is excited
and become more permeable, allowing more ions to move in and out
of the cell – altering the potential difference. The change in potential
difference due to a stimulus is called the generator potential.
• A bigger stimulus excites the membrane more, causing a bigger
movement of ions and a bigger change in potential difference – so a
bigger generator potential is generated.
• If the generator potential is big enough it’ll trigger as action potential
(nerve impulse) along a neuron. An action potential is only triggered if
the generator difference reaches a certain threshold level.
• If the stimulus is too weak the generator potential won’t reach the
threshold, so there’s no action potential.
Resting potential
• In a neurons resting state, the outside of the
membrane is positively charged compared to the
inside. This is because there are more positive ions
outside than inside.
The membrane is
polarized, with a
voltage difference.
Resting potential is
maintained by sodium
potassium pumps and
potassium ion
channels.
Depolarizing
• A stimulus causes the sodium ion channels to open. The membrane
becomes more permeable to sodium. This makes inside the cell less
negative.
• When the potential reaches a threshold, voltage-gated sodium ion
channels open and more sodium ions diffuse into the neuron.
• This makes inside the cell negative.
Figure 48.12-2
Axon
Plasma
membrane
Action
potential
1
Na
K
2
Cytosol
Action
potential
Na
K
Repolarization
• At a potential difference around 30 mV the sodium ion channels close
and the voltage potassium channels open.
• The membrane is then more permeable to potassium so potassium
ions diffuse out of the neuron down the concentration gradient. This
starts to get the membrane back to its resting potential.
Resting potential
• The ion channels are reset. The sodium potassium pump returns the
membrane to its resting potential and maintains it until the
membranes excited by another stimulus.
Figure 48.12-3
Axon
Plasma
membrane
Action
potential
1
Na
K
2
Cytosol
Action
potential
Na
K
K
3
Action
potential
Na
K
#7 – Sensory receptors convert stimulus energy into
nerve impulses
When a nerve impulse reaches the end of a neuron
chemicals called neurotransmitters take the
information across to the next neuron, which then
sends a nerve impulse.
The action potential causes the release of the
neurotransmitter
The neurotransmitter diffuses across the synaptic cleft
and is received by the postsynaptic cell
At chemical synapses, a chemical neurotransmitter
carries information across the gap junction
The CNS processes the information, decides what to
do about it and sends impulses along motor neurons
to an affector.
Figure 48.15
Presynaptic
cell
Postsynaptic cell
Axon
Synaptic vesicle
containing
neurotransmitter
1
Postsynaptic
membrane
Synaptic
cleft
Presynaptic
membrane
3
K
Ca2 2
Voltage-gated
Ca2 channel
Ligand-gated
ion channels
4
Na
Animation: Synapse
Right-click slide / select “Play”
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The Endocrine System
Chapter 45
#1 Function of the Endocrine System
• Animal hormones are chemical signals that are
secreted into the circulatory system and communicate
regulatory messages within the body
• Hormones reach all parts of the body, but only target
cells have receptors for that hormone
• The endocrine system secretes hormones that
coordinate slower but longer-acting responses
including reproduction, development, energy
metabolism, growth, and behavior
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#2 - Endocrine Tissues and Organs
• In some tissues, endocrine cells are grouped together
in ductless organs called endocrine glands
• Endocrine glands secrete hormones directly into
surrounding fluid
• These contrast with exocrine glands, which have ducts
and which secrete substances onto body surfaces or
into cavities
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Figure 45.4
Major endocrine glands:
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
(behind thyroid)
Organs containing
endocrine cells:
Thymus
Heart
Liver
Adrenal glands
(atop kidneys)
Stomach
Pancreas
Kidneys
Ovaries (female)
Small
intestine
Testes (male)
Chemical Classes of Hormones
• Three major classes of molecules function as
hormones in vertebrates
• Polypeptides (proteins and peptides)
• Amines derived from amino acids
• Steroid hormones
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• Lipid-soluble hormones (steroid hormones) pass easily
through cell membranes, while water-soluble
hormones (polypeptides and amines) do not
• The solubility of a hormone correlates with the
location of receptors inside or on the surface of target
cells
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Table 45.1a
Table 45.1b
Feedback Regulation
• A negative feedback loop inhibits a response by
reducing the initial stimulus, thus preventing excessive
pathway activity
• Positive feedback reinforces a stimulus to produce an
even greater response
• For example, in mammals oxytocin causes the release
of milk, causing greater suckling by offspring, which
stimulates the release of more oxytocin
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Insulin and Glucagon: Control of Blood
Glucose
• Insulin (decreases blood glucose) and glucagon
(increases blood glucose) are antagonistic hormones
that help maintain glucose homeostasis
• The pancreas has clusters of endocrine cells called
pancreatic islets with alpha cells that produce
glucagon and beta cells that produce insulin
© 2011 Pearson Education, Inc.
Figure 45.13
Insulin
Body cells
take up more
glucose.
Blood glucose
level declines.
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level rises
(for instance, after eating a
carbohydrate-rich meal).
Homeostasis:
Blood glucose level
(70–110 mg/m100mL)
STIMULUS:
Blood glucose level
falls (for instance, after
skipping a meal).
Blood glucose
level rises.
Liver breaks
down glycogen
and releases
glucose into
the blood.
Alpha cells of pancreas
release glucagon into
the blood.
Glucagon
Figure 45.13a-1
Insulin
Beta cells of
pancreas
release insulin
into the blood.
STIMULUS:
Blood glucose level rises
(for instance, after eating a
carbohydrate-rich meal).
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
Figure 45.13a-2
Insulin
Body cells
take up more
glucose.
Blood glucose
level declines.
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
STIMULUS:
Blood glucose level rises
(for instance, after eating a
carbohydrate-rich meal).
Figure 45.13b-1
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
STIMULUS:
Blood glucose level
falls (for instance, after
skipping a meal).
Glucagon
Alpha cells of pancreas
release glucagon into
the blood.
Figure 45.13b-2
Homeostasis:
Blood glucose level
(70–110 mg/100 mL)
STIMULUS:
Blood glucose level
falls (for instance, after
skipping a meal).
Blood glucose
level rises.
Liver breaks
down glycogen
and releases
glucose into
the blood.
Glucagon
Alpha cells of pancreas
release glucagon into
the blood.
#7. Target Tissues for Insulin and
Glucagon
• Insulin reduces blood glucose levels by
• Promoting the cellular uptake of glucose
• Slowing glycogen breakdown in the liver
• Promoting fat storage, not breakdown
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• Glucagon increases blood glucose levels by
• Stimulating conversion of glycogen to glucose in the
liver
• Stimulating breakdown of fat and protein into
glucose
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Diabetes Mellitus
• Diabetes mellitus is perhaps the best-known
endocrine disorder
• It is caused by a deficiency of insulin or a decreased
response to insulin in target tissues
• It is marked by elevated blood glucose levels
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• Type 1 diabetes mellitus (insulin-dependent) is an
autoimmune disorder in which the immune system
destroys pancreatic beta cells
• Type 2 diabetes mellitus (non-insulin-dependent)
involves insulin deficiency or reduced response of
target cells due to change in insulin receptors
© 2011 Pearson Education, Inc.